Abstract

There were two purposes to the work of this thesis (a) to identify the role of isometrictraining intensity in the training-induced reductions in resting blood pressure, and (b) toidentify whether the mechanism for the reduced resting blood pressure is best reflectedin what can be broadly termed cardiovascular, neuromuscular or metabolic markers ofthat training. Firstly, in a cross-sectional study, the only strong correlation was foundbetween heart rate variability (a cardiovascular marker) and resting blood pressure.Secondly, this cardiovascular marker was also significantly affected by a single sessionof isometric exercise, an effect that persisted for at least 4 hours after exercise. However,thirdly, this marker and other cardiovascular markers (such as cardiac output and strokevolume) did not correlate with reductions in blood pressure seen after 4 weeks ofisometric training. Instead, the training-induced reductions in blood pressure correlatedstrongly with neuromuscular and metabolic markers of isometric training. The extent towhich local muscle fatigue was induced during isometric training correlated with thereductions in resting blood pressure. Therefore (a) isometric training intensity appears tobe of utmost importance in the reductions in resting blood pressure (when bilateral-legexercise is performed in 2 minute bouts), and (b) the mechanism whereby theadaptations in resting blood pressure occur is best reflected in neuromuscular andmetabolic markers of local muscle fatigue during that training. These findings arediscussed with a particular focus on the possible role of muscle metaboreceptorstimulation, during isometric training in the mechanism of training-induced reduction inresting blood pressure.